Density Functional Theory (DFT) Investigation of Thiophene-Pyrrole Copolymers for VOC and Inorganic Gas Sensing Applications

This study presents a comprehensive DFT-based investigation of thiophene-pyrrole copolymers (1PT, 2PT, and 3PT) as sensing materials for volatile organic compounds (VOCs) and inorganic gases, including NH₃, CHCl₃, CO₂, and CH₂O₂. The structural optimization, interaction energies, natural bond orbital (NBO) charge analysis, HOMO-LUMO band gap, and TD-DFT simulated UV-Vis spectra were analyzed using the B3LYP functional and 6-31G(d) basis set. Among the analytes, ammonia exhibited the highest interaction energy (−10.60 kcal/mol) with the 3PT copolymer, indicating strong hydrogen bonding. NBO results further validated significant charge transfer, particularly in 2PT complexes. A red shift in UV-Vis absorption spectra confirmed enhanced conductivity and sensing potential. This study supports the use of thiophene-pyrrole copolymers as cost-effective and highly sensitive materials for gas sensor development.